I think TLJ is naturally an easy film to hate on. When one is watching it, it is new and takes lots of turns. One might initially completely dig it and the feelings it encompasses, but these feelings do not stay. Shrugging off TLJ months later is a lazy thing to do, but I foresee a lot of hardcore fans doing that.
The Phantom Menace, Titanic, and Avatar are other films that were widely loved only to be thrown into the back of the head when it comes to surface conversation.
I think this same surface disapproval of TLJ's legacy will be easy for a lot of people just because of the basic eliminations the first made for the franchise.
It is like asking random people what they think of politics, and they shrug.
Imagine watching cartoons with the kids and refreshing the kids on how great the movie is only to forget about it. Or associating an experience with a bad memory, or feeling meh about The Hobbit trilogy after the last one and then forgetting the movement it brought.
If anything, TLJ was overstuffed with plot turns and it didn't flow as smooth as the others. But I think rejecting TLJ would be like thinking back on something that supposedly universally 'sucked' and agreeing with the universe that it sucked.